Methods and system for hopset selection

ABSTRACT

A communication method includes obtaining power data associated with a plurality of channels of a frequency band and determining a counter of a set of signal-to-noise ratios (SNRs) for each of the plurality of channels. The set of SNRs is calculated based at least in part on power data for the each of the plurality of channels. The method further includes predicting an error rate for each of the plurality of channels based at least in part on the counter and selecting a hopset of channels for frequency hopping from the plurality of channels based at least in part on the predicted error rates for the plurality of channels.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/671,878,filed Nov. 1, 2019, which is a continuation of International ApplicationNo. PCT/CN2017/083289, filed May 5, 2017, the entire contents of both ofwhich are incorporated herein by reference.

BACKGROUND OF THE DISCLOSURE

Modern unmanned aerial vehicles (UAVs) are used to perform a variety oftasks such as navigation, surveillance and tracking, remote sensing,search and rescue, scientific research, and the like. However, providinginterference-resistant communication for UAVs remains a challenge.

SUMMARY OF THE DISCLOSURE

According to embodiments, a computer-implemented method forcommunication is provided. The method comprises obtaining power dataassociated with a plurality of channels of a frequency band; predictingan error rate for each of the plurality of channels based at least inpart on the power data; and selecting a hopset of channels for frequencyhopping from the plurality of channels based at least in part on thepredicted error rates for the plurality of channels.

According to embodiments, an unmanned aerial vehicle (UAV) is provided.The UAV comprises a memory that stores one or more computer-executableinstructions; and one or more processors configured to access the memoryand execute the computer-executable instructions to perform a methodcomprising: obtaining power data associated with a plurality of channelsof a frequency band; predicting an error rate for each of the pluralityof channels based at least in part on the power data; and selecting ahopset of channels for frequency hopping from the plurality of channelsbased at least in part on the predicted error rates for the plurality ofchannels.

According to embodiments, a communication system is provided. Thecommunication system comprises a memory that stores one or morecomputer-executable instructions; and one or more processors configuredto access the memory and execute the computer-executable instructions toperform a method comprising: obtaining power data associated with aplurality of channels of a frequency band; predicting an error rate foreach of the plurality of channels based at least in part on the powerdata; and selecting a hopset of channels for frequency hopping from theplurality of channels based at least in part on the predicted errorrates for the plurality of channels.

According to embodiments, one or more non-transitory computer-readablestorage media is provided for storing computer executable instructionsthat, when executed by a computing system, configure the computingsystem to perform operations comprising: obtaining power data associatedwith a plurality of channels of a frequency band; predicting an errorrate for each of the plurality of channels based at least in part on thepower data; and selecting a hopset of channels for frequency hoppingfrom the plurality of channels based at least in part on the predictederror rates for the plurality of channels.

In some embodiments, the power data associated with the plurality ofchannels comprises power spectral density (PSD) data. The PSD dataassociated with the plurality of channels may comprise noise powerspectral density (NPSD) data and/or signal power spectral density (SPSD)data.

In some embodiments, obtaining the power data comprises selecting a setof one or more measurement channels from the plurality of channels,wherein channel bandwidths of the set of measurement channelscollectively cover the frequency band; obtaining power data for each ofthe set of measurement channels; and obtaining power data for theplurality of channels using the power data for the set of measurementchannels.

In some embodiments, the plurality of channels comprises a first channeland a second channel, wherein the first channel is in the set ofmeasurement channels, and the second channel is not in the set ofmeasurement channels.

In some embodiments, the first channel and the second channel overlapand power data for the second channel is obtained based on the powerdata for the first channel.

In some embodiments, predicting the error rate for each of the pluralityof channels comprises calculating a set of signal-to-noise ratios (SNRs)for the channel based at least in part on the power data for thechannel; determining a counter of the set of SNRs based on a SNRthreshold; and predicting the error rate based at least in part on thecounter.

In some embodiments, the counter indicates a number of the SNRs thatexceed the SNR threshold.

In some embodiments, selecting the hopset of channels comprisesselecting a predetermined number of channels from the plurality ofchannels by comparing the predicted error rates for the plurality ofchannels with one or more predetermined thresholds.

In some embodiments, the hopset of channels is used by a UAV to receivesignals from a remote terminal via an uplink.

In some embodiments, the hopset is transmitted to the remote terminalvia a downlink with the remote terminal.

In some embodiments, a channel is selected from the hopset for receivingsignals from the remote terminal based on a function of the hopset and atimestamp.

It shall be understood that different aspects of the disclosure can beappreciated individually, collectively, or in combination with eachother. Various aspects of the disclosure described herein may be appliedto any of the particular applications set forth below or datacommunication between any other types of movable and/or stationaryobjects.

Other objects and features of the present disclosure will becomeapparent by a review of the specification, claims, and appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present disclosure will be obtained by reference tothe following detailed description that sets forth illustrativeembodiments, in which the principles of the disclosure are utilized, andthe accompanying drawings of which:

FIG. 1 illustrates an exemplary communication system for implementinghopset selection, in accordance with embodiments.

FIG. 2 illustrates exemplary processes for implementing frequencyhopping, in accordance with embodiments.

FIG. 3 illustrates an exemplary process for selecting a hopset, inaccordance with embodiments.

FIG. 4 illustrates an exemplary process for selecting a hopset, inaccordance with embodiments.

FIG. 5 illustrates an exemplary process for obtaining power dataassociated with a plurality of channels, in accordance with embodiments.

FIG. 6 illustrates an exemplary frequency band with a plurality ofchannels, in accordance with embodiments.

FIG. 7 illustrates obtaining power data for exemplary overlappingchannels, in accordance with embodiments.

FIG. 8 illustrates an exemplary spectrogram showing power data overtime, in accordance with embodiments.

FIG. 9 illustrates portions of an exemplary spectrogram in detail.

FIG. 10 illustrates an exemplary process for predicting error rate of achannel, in accordance with embodiments.

FIG. 11 illustrates an exemplary process for selecting a hopset ofchannels, in accordance with embodiments.

FIG. 12 illustrates a movable object including a carrier and a payload,in accordance with embodiments.

FIG. 13 is a schematic illustration by way of block diagram of a systemfor controlling a movable object, in accordance with embodiments.

DETAILED DESCRIPTION OF THE DISCLOSURE

Frequency-hopping (FH) techniques have been used to resist interferenceand reduce noise in radio communication. Noise generally refers tounwanted influence on signals (e.g., white noise) such as caused bythermal noise, electronic noise from receiver input circuits, orinterference from radiated electromagnetic noise picked up by thereceiver's antenna. In a FH scheme, an available frequency band (e.g.,the 2.4 GHz band) is divided into a plurality of communication channels.Each of the channels is associated with a given sub-frequency within thefrequency band and a channel bandwidth. The carrier frequency used totransmit radio signals can be configured to rapidly change or “hop”among these sub-frequencies (or channels) in an order (e.g.,predetermined or pseudorandom) known to both the transmitting device andthe receiving device. Thus, interference at a particular frequency onlyaffects the signal during the short interval during which that frequencyis used to transmit the signal.

To improve performance, the set of channels or frequencies used forfrequency hopping (hereinafter “hopset”) may be configured to changeadaptively according to the characteristics of the communicationenvironment surrounding the communication devices. Such characteristicsmay include noise power, signal power, signal-to-noise ratio (SNR), andthe like. For instance, channels with strong interference or low SNR maybe removed from a hopset while channels with strong interference or highSNR may be added to the hopset. The changing hopset can be synchronizedbetween transmitting and receiving devices.

According to embodiments, techniques are provided for improvingcommunication using frequency hopping. Power data associated with aplurality of channels of a frequency band can be obtained over a periodof time. Error rate for each of the plurality of channels can bepredicted based at least in part on the power data. Subsequently, ahopset of channels for frequency hopping can be selected from theplurality of channels based at least in part on the predicted errorrates for the channels.

According to embodiments, techniques are provided for efficientlyobtaining power data of channels. Rather than measuring the power datafor every available channel within the frequency band, only some of thechannels are measured. In some embodiments, a set of one or moremeasurement channels is selected from the plurality of channels, suchthat the channel bandwidths of the measurement channels collectively andsubstantially cover the frequency band. Power data for each of themeasurement channels is obtained and combined to generate the power datafor the plurality of channels. Accordingly, the power data for theentire frequency band can be obtained in less time than when everychannel within the frequency band is measured. Further, faster channelmeasurement means more reliable measurement results used for hopsetselection, thereby improving the reliability of the frequency hoppingscheme.

According to embodiments, techniques are provided for improving theaccuracy and efficiency of hopset selection. In particular, the channelsin the hopset are selected based on their respective, predicted errorrates. In some embodiments, the error rates to be experienced by thechannels can be predicted based on recent noise power data and/oraverage signal power. The channels with low predicted error rates can beselected in hopset for frequency hopping. The techniques describedherein provide fast and relatively accurate estimation of the errorrates to be experienced by the channels, thereby improving theperformance of the frequency hopping scheme.

According to aspects of embodiments, techniques are provided forefficient synchronization of the hopset between transmitting andreceiving devices. For example, the hopset can be transmitted betweendevices with an effective time. As another example, the hopset may beupdated in response to a triggering event such as a change in theinterference environment. As yet another example, a channel can beselected from the hopset use based on a function of the hopset and atimestamp.

FIG. 1 illustrates an exemplary communication system 100 forimplementing hopset selection, in accordance with embodiments. Thecommunication system 100 comprises a frequency hopping (FH) receivingdevice 102 and a frequency hopping (FH) transmitting device 104. The FHreceiving device 102 can be configured to receive signals transmitted bythe FH transmitting device 104 using a FH link 108. The FH transmittingdevice 104 can be configured to receive signals transmitted by the FHreceiving device 102 using a reverse link 106. The FH link 108 and thereverse link 106 can be any wireless communication links such as radiolinks. The FH link 108 can utilize a frequency hopping scheme. Thereverse link 106 may or may not use frequency hopping.

In some embodiments, the FH receiving device 102 and the FH transmittingdevice 104 may be configured to receive and transmit signals using aplurality of channels within a certain frequency band (e.g., the 2.4 GHzband). In some embodiments, the FH receiving device 102 can beconfigured to obtain (e.g., measure, estimate, and/or calculate) powerdata (e.g., noise power and/or signal power) of the channels within thefrequency band and to generate or update a hopset of channels based onthe power data. The hopset may be transmitted by the FH receiving device102 to the FH transmitting device 104 via the reverse link 106.Subsequently, the FH receiving device 102 and the FH transmitting device104 may be configured to communicate over the FH link 108 by hoppingamong the channels in the hopset.

In some embodiments, the FH receiving device 102 may be an uplinkdevice. The FH transmitting device 104 may be a downlink device. The FHlink 108 may be an uplink. The reverse link 106 may be a downlink. Inother embodiments, the FH receiving device 102 may be a downlink device.The FH transmitting device 104 may be an uplink device. The FH link 108may be a downlink. The reverse link 106 may be an uplink.

In some embodiments, the FH receiving device 102 can include or beincluded by an unmanned aerial vehicle (UAV) or any other movable objectdescribed herein. The FH transmitting device 104 can include or beincluded by a remote terminal such as a ground station, a remotecontroller, a mobile device, and the like. In some other embodiments,the FH receiving device 102 can include or be included by a remoteterminal such as a ground station, a remote controller, a mobile device,and the like. The FH transmitting device 104 can include or be includedby an unmanned aerial vehicle (UAV) or any other movable objectdescribed herein.

FIG. 2 illustrates exemplary processes 200A and 200B for implementingfrequency hopping, in accordance with embodiments. Some or all aspectsof the process 200 (or any other processes described herein, orvariations and/or combinations thereof) may be performed by one or moreprocessors associated with the FH receiving device 102 and/or the FHtransmitting device 104. Some or all aspects of the process 200 (or anyother processes described herein, or variations and/or combinationsthereof) may be performed under the control of one or morecomputer/control systems configured with executable instructions and maybe implemented as code (e.g., executable instructions, one or morecomputer programs or one or more applications) executing collectively onone or more processors, by hardware or combinations thereof. The codemay be stored on a computer-readable storage medium, for example, in theform of a computer program comprising a plurality of instructionsexecutable by one or more processors. The computer-readable storagemedium may be non-transitory. The order in which the operations aredescribed is not intended to be construed as a limitation, and anynumber of the described operations may be combined in any order and/orin parallel to implement the processes.

Turning first to process 200A of FIG. 1. At block 202, a hopset ofchannels for frequency hopping is selected based on predicted errorrates of the channels. For examples, channels with lower predicted errorrates may be selected into the hopset; while channels with higherpredicted error rates may be excluded from the hopset. In someembodiments, the selection of the hopset may be implemented by an FHreceiving device 102 shown in FIG. 1. In other embodiments, theselection of the hopset may be implemented by other devices. Moredetailed discussion of hopset selection is provide elsewhere herein,e.g., in connection with FIGS. 4-9.

At block 204, the selected hopset is synchronized between transmittingand receiving devices, such that both devices have the same hopset foruse with frequency hopping. For instance, the hopset can be transmittedby the FH receiving device 102 to the FH transmitting device 104 shownin FIG. 1. More detailed discussion related to hopset synchronization isprovided elsewhere herein.

At block 206, the hopset is used for transmitting and/or receivingsignals using frequency hopping techniques. For example, the FHtransmitting device 104 and the FH receiving device 102 may beconfigured to “hop” among the channels in the hopset for signaltransmission and reception, respectively. The frequency hopping betweenthe transmitting and the receiving devices need to be synchronized, suchthat signals transmitted using a given channel is also received at thatchannel. More detailed discussion related to channel synchronization isprovided elsewhere herein.

Turning to process 200B of FIG. 1. At block 208, a hopset is updated inresponse to a change in the environment, such as an increase/decrease ininterference or signal-to-noise ratio (SNR). For example, the hopset maybe updated when the SNR reaches a predetermined threshold value. In someembodiments, the hopset may be updated based on predicted error rates ofthe channels as describe in further detail elsewhere herein. Forinstance, one or more channels may be removed from the hopset due totheir increased error rates for the channels. Conversely, one or morechannels may be added to the hopset due to their lowered error rates.

At block 210, the updated hopset is synchronized between transmittingand receiving devices, such that both devices have the same hopset foruse with frequency hopping. The block 210 may be implemented in asimilar manner as for block 204 of process 200A. At block 212, thehopset is used for transmitting and/or receiving signals using frequencyhopping techniques. The block 210 may be implemented in a similar manneras for block 206 of process 200A.

FIG. 3 illustrates an exemplary process 300 for selecting a hopset, inaccordance with embodiments. The horizontal axis shows time of signaltransmission starting from T1 and the vertical axis shows thefrequencies or channels in a frequency band or spectrum, starting fromC1. The shaded areas illustrate the frequencies or channels used totransmit signals at given time slots. For example, at T1, the channel C1is used to transmit signals. A first hopset (hopset 1) comprisingchannels C1, C2, C3, C4, and C5 is used to transmit signals starting atT1. The order in which the channels within the hopset are selected maybe predetermined or pseudorandom. The exemplary order shown in FIG. 3 isC1, C4, C2, C5, and C3 at T1, T2, T3, T4, and T5, respectively. However,due to changes in the characteristics of the communication environment,channels/frequencies from the first hopset may be added and/or removed.For instance, the power data at some or available channels may beobtained and the channels with the low predicted error rate may beselected. The newly selected channels may form an updated hopset 2.Compared with hopset 1, hopset 2 can include addition channelsdetermined to have relatively low error rates, noise or interference(e.g., C6, C8, and C10), while excluding channels determined to haverelatively high error rates, noise or interference (e.g., C2 and C3). Byadaptively changing the hopset according to the characteristics of thecommunication environment, the overall performance of the frequencyhopping scheme can be improved.

FIG. 4 illustrates an exemplary process 400 for selecting a hopset, inaccordance with embodiments. Aspects of the process 400 may be performedby one or more processors associated with the FH receiving device 102,the FH transmitting device 104, or both.

At block 402, power data associated with a plurality of channels(frequencies) within a frequency band is obtained over a period of time.In some embodiments, the power data may be obtained according to theprocess 500 of FIG. 5. FIGS. 7-8 illustrate exemplary obtained powerdata.

At block 404, an error rate is predicted for each of the plurality ofchannels based at least in part on the power data obtained above. Insome embodiments, the error rates may be predicted according to theprocess 900 of FIG. 9.

The error rates may be predicted using alternative methods. In anembodiment, the error rate is predicted based on a number of times orpercentage of measurement results where the noise or interference power(e.g., NPSD) exceeds a predetermined threshold. In another embodiment,for channels/frequencies that are or were in a hopset, the predictederror rate can be based on the statistical analysis of the error ratesin data transmission (e.g., block error rate (BLER)).

At block 406, a hopset of channels is selected from the plurality ofchannels based at least in part on the predicted error rates of thechannels. In some embodiments, the hopset may be selected according tothe process 1000 of FIG. 10.

The hopset may be selected using alternative methods. For example, thehopset can be selected based at least in part on a geographic locationof the communication environment (e.g., a geographic location of the FHreceiving device such as a UAV). For example, certain channels may havestrong interference at certain geographic locations, and hence shouldnot be selected in the hopset. Conversely, certain channels may havelittle interference at certain geographic locations, and hence should beincluded. The rules governing the inclusion or exclusion of the channelsbased on geographic locations nay be stored locally (e.g., in a memoryassociated with a FH receiving device such as a UAV), or in a networkdevice (e.g., a cloud-based storage device). As another example, a givengeographic location may be associated with a given hopset. Theassociation between geographic locations and the hopsets may be storedlocally (e.g., in a memory associated with a FH receiving device such asa UAV), or in a network device (e.g., a cloud-based storage device).

In some embodiments, the power data for the channels is measured andcalculated on a continuous or periodic basis. Therefore, when thecommunication environment changes, such change can be quickly detectedbased on the power data and the hopset can be timely updated, wherenecessary. Subsequently, the updated to the hopset may be synchronizedacross devices to enable frequency hopping based on the updated hopset.

FIG. 5 illustrates an exemplary process 500 for obtaining power dataassociated with a plurality of channels, in accordance with embodiments.Aspects of the process 500 may be performed by one or more processorsassociated with the FH receiving device 102, the FH transmitting device104, or both.

At block 502, a set of one or more measurement channels are selectedfrom a plurality of channels within a given frequency band, such thatthe channel bandwidths of the measurement channels collectively coverthe frequency band. In this disclosure, the set of one or moremeasurement channels is also referred to as a “measurement set.” Thechannel bandwidth(s) of the one or more measurement channels in themeasurement set collectively form a collective set bandwidth.

Turning now to FIG. 6, which illustrates an exemplary frequency bandwith a plurality of channels. As illustrated, the 2.4 GHz frequency band(from 2.4 GHz to 2.4835 GHz) is divided into 14 channels with respectivecenter frequencies ranging from 2.412 GHz to 2.484 GHz. For eachmeasurement channel, the bandwidth of the receiving signals (channelbandwidth) is about 22 MHz. While the channels shown in FIG. 6 haveidentical channel bandwidth, it is understood that in other embodiments,the channels may have different channel bandwidths. For instance,channel 1 is centered at frequency 2.412, channel 2 is centered atfrequency 2.417, and so on. Thus, the channel bandwidths of some of thechannels overlap. Instead of measuring channel conditions (e.g., powerdata) for all channels, only a subset of the channels can be measured toderive the condition for the whole frequency band. The collectivebandwidths of the selected measurement channels substantially cover thefrequency band. Substantially covering the frequency band may includecovering 100% of the frequency band, or covering up to or more than 50%,60%, 70%, 80%, 90%, or 95% of the frequency band.

For example, in the embodiment 600A, channels 1, 5, 9, and 13 areselected for measurement. These channels substantially cover the 2.4 GHzfrequency band. A non-selected channel may overlap with at least oneselected channel. Therefore, the power data for the non-selectedchannels (e.g., channels 2, 3, 4, 6, 7, 8, 10, 11, 12) may be estimatedusing the power data for the selected channels. For example, thenon-selected channel 2 overlaps with the selected channel 1 at spectrum602. Thus, the power data for channel 1 at spectrum 602 can be used forthe power data for channel 2 at spectrum 602. Similarly, channel 2overlaps with the selected channel 5 at spectrum 604. Thus, the powerdata for channel 5 at spectrum 604 can be used for the power data forchannel 2 at spectrum 604. Thus, the power data for the entire channelbandwidth of channel 2 can be obtained by combining the power data forthe channel 1 and the power data for channel 5.

In some embodiments, at least two adjacent measurement channels mayoverlap so as to enable more reliable coverage for the frequency band.The power data for an overlap portion between a first channel and asecond channel can be based on the power data of the first channel, thepower data of the second channel, or both. For example, adjacentmeasurement channels 5 and 9 overlap at portion 606. The power data forthe portion 606 can be the power data of channel 5 that corresponds tothe option 606, the power data of channel 9 that corresponds to theoption 606, or a combination (e.g., a linear combination such as anaverage) of both.

In some embodiments, increasing the number of measurement channels canincrease the reliability of measurement data. For example, in theembodiment 600B, channels 1, 4, 7, 10, and 13 are selected formeasurement. These channels substantially cover the 2.4 GHz frequencyband and provide wider overlap between selected channels than shown inthe embodiment 600A. For example, the overlap portion 608 in embodiment600B is wider than the overlap portion 606 in embodiment 600A. A wideroverlap means multiple measurement results are available for a largerportion of the spectrum, enabling a more accurate and reliableestimation for the overlap portion.

In some embodiments, such as 600C, at least two adjacent measurementchannels do not overlap. As illustrated, channels 1, 6, 11, and 14 maybe selected for measurement. The selection of channel 14 may beoptional. Adjacent channels 1 and 6 do not overlap. Similarly channels 6and 11 do not overlap. In such embodiments, power data for a portionthat does not have direct measurement data may be obtained based onmeasurement data from neighboring regions. For example, the power datafor the gap 610 between channel 1 and channel 6 can be estimated usingthe power data for channel 1, the power data for channel 6, or both. Forexample, the power data for the gap 610 may be calculated as an averageof the power data of the channel 1 and the power data of the channel 6.

As discussed herein, the selective measuring of some, but not all, ofthe channels within a frequency band can shorten the amount of time, aswell as the amount of processing, required to estimate power data for anentire frequency band. In some examples, the reduction in processingtime or workload can be around 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%,80%, or 90% compared with full measurement or scan of all the channels.Additionally, the reduced processing time means that the processingresults are more likely to be up-to-date, reflecting the actualenvironment (which may change over time). Thus, the results are likelymore reliable than those obtained using the full scan.

Referring back to FIG. 5, at block 504, power data for each measurementchannel is obtained. The power data may be estimated at a predeterminedresolution such as 1 MHz. That is, the power data is estimated for every1 MHz within the channel bandwidth. The measurement resolution may beconfigurable (e.g., by a user). Measurement at a higher resolutionyields more reliable results but takes longer time, while measurement ata lower resolution yields less reliable results but takes shorter time.

In some embodiments, power data may include power spectral density (PSD)data, which describes the distribution of power into frequencycomponents of the signals. The power data can include power data for theintended signals, such as signal power spectral data (SPSD).Alternatively or additionally, the power data can include power data fornoise such as noise power spectral data (NPSD).

Obtaining power data may include measuring, transforming, estimating, orotherwise processing data related to power. For example, any suitablespectral density estimation (SDE) techniques can be used to estimate thespectral density of a signal from a sequence of time samples of thesignal. Such techniques can include non-parametric and parametric SDEtechniques. Non-parametric SDEs can include periodogram, Bartlett'smethod, Welch's method, multitaper, lease-squares spectral analysis,non-uniform discrete Fourier transform, singular spectrum analysis,short-time Fourier transform, and the like. Parametric SDEs can includeautoregressive model (AR) estimation, moving-average (MA) model,autoregressive moving average (ARMA) estimation, maximum entropyspectral estimation, and the like.

At block 506, power data for the plurality of channels is obtained usingthe power data for the measurement set of channels. As discussedearlier, once the power data for the selected measurement channels isobtained, the power data for the non-selected channels may be obtainedbased on the power data for the selected channels. For example, if anon-select channel overlaps with a selected channel, the power data forthe selected channel over the overlap portion can be used as the powerdata for the non-select channel for the overlap portion. If a non-selectchannel does not overlap with a selected channel, the power data for theclosest selected channel(s) can be used to estimate the power data forthe non-select channel (e.g., by taking an average). Power data for twooverlapping portions, a first portion and a second portion, can becalculated based on the power data for the first portion, the power datafor the second portion, or both.

FIG. 7 illustrates obtaining power data for exemplary overlappingchannels C1 and C2, in accordance with embodiments. The Channels C1 andC2 overlaps at 704. Channel C1 is selected for measurement at aresolution 702. F5 is the center frequency for channel C1. For example,assuming the channel bandwidth of C1 is 8 MHz, and the resolution 702 is1 MHz, then the power data is measured at frequencies Fl to F9 which are1 MHz apart. As illustrated, when F5 is selected for measurement, thenon-selected frequencies, F1-F4 and F6-F9 are also measured.

Assuming C2 (with center frequency F10) has the same channel bandwidthand measurement resolution as C1, then C2 is measured at frequencies F6to F14, also 1 MHz apart. Thus, when F10 is selected for measurement,the non-selected frequencies, F6-F9 and F11-F14 are also measured. Thefrequencies falling within the overlapping portion 704 between C1 andC2, F6-F9 are measured twice, once when C1 is measured and again for C2is measured. The power data at a frequency in the overlapping portion704 (e.g., F6, F7, F8, or F9) can be obtained based on the power data ofC1 at that frequency, the power data of C2 at that frequency, or both(e.g., an average). Thus, the reliability measurement for theoverlapping portion is higher than the non-overlapping portions. WhileC1 and C2 are shown in FIG. 7 to have the same channel bandwidth andmeasurement resolution, it is understood that the selective measurementtechniques described herein apply to other embodiments where measurementchannels have different channel bandwidth and/or measurementresolutions.

In some embodiments, the power data obtained herein can be used togenerate a spectrogram, which may then be used to determine the hopset.FIG. 8 illustrates an exemplary spectrogram 800 showing power spectraldensity (PSD) data with respect to time, in accordance with embodiments.The x-axis denotes time (e.g., in milliseconds) and the y-axis denotesfrequency (e.g., in MHz). For each (time, frequency) point in thespectrogram, a grayscale value indicates the corresponding PSD value indBM/MHz according to the grayscale 802, where higher PSD valuescorrespond to higher grayscale values (darker), and lower PSD valuescorrespond to lower grayscale values (lighter). At any given point intime, the frequencies selected to be in a hopset is denoted in bold.

FIG. 9 illustrates portions of the exemplary spectrogram 800 in detail.The power density information associated with each (time, frequency)unit is represented by the corresponding grayscale value. The bolded boxaround a (time, frequency) unit indicates that the frequency is selectedin the hopset for use by frequency hopping. For example, at time T1, T2,T3 and T4, the hopset includes F2, F3, F4 and F5. At T5 and T6, thehopset is updated to includes F1, F2, F3, and F5. As illustrated, thePSD for F1 decreases over time, indicating decreasing interference atF1, until the interference is low enough for F1 to be added to thehopset at T5. On the other hand, the PSD for F4 increases over time,indicating increasing interference at F5, until the interference is highenough for F4 to be removed from the hopset at T5. In some embodiments,the spectrogram may be generated based on measurement results and usedto predict error rates and to select a hopset as described in FIGS.10-11.

According to embodiments, the channels in a hopset can be selectedaccording to predicted error rates. The error rates can be predictedbased on power data indicating interference and/or power data indicatingsignal strength. In particular, the prediction of error rates leveragesa series of measurement results from recent measurements, therebyimproving accuracy and reliability of the prediction.

FIG. 10 illustrates an exemplary process 1000 for predicting error rateof a channel, in accordance with embodiments. Aspects of the process1000 may be performed by one or more processors associated with the FHreceiving device 102, the FH transmitting device 104, or both.

At block 1002, a set of signal-to-noise ratios (SNRs) are calculated foreach of the plurality of channels based at least in part on the powerdata for that channel. The power data may be obtained using methodsdescribed in FIGS. 5-9.

For example, for a given channel c, at a given time t, the interferencepower measured at the most recent M measurements is P_(I)(m); m=1, 2, .. . , M , where M is an integer greater than or equal to 1. Let averageP _(s) denotes the average signal power at time t, thenSNR(m)=10*log₁₀(P _(s)/P_(I)(m)); m×1, 2, . . . , M. In someembodiments, the interference power and/or the average signal power canbe obtained using the selective measurement techniques as describedherein (e.g., in FIGS. 5-8).

At block 1004, a counter of the set of the SNRs is determined based onan SNR threshold. For example, the counter M′ can denote the number oftimes when SNR(m)<T, where T is an SNR threshold. The threshold T can bedetermined based on experiments or simulation. In an example, the valueT can be the value of SNR when the error rate around 50% in a channelunder an additive white Gaussian noise (AWGN) model. That is, whenSNR<T, the block error rate (BLER) is greater than 50%. Because BLERdecreases sharply from 100% to 50%, it can be assumed approximately thaterror has occurred when SNR<T. Conversely, when SNR>T, BLER<50%. BecauseBLER decreases sharply from 50% to 0%, it can be assumed approximatelythat error has not occurred when SNR>T.

In some embodiments, the SNR threshold T can be adjusted based on realscenarios. For example, the SNR threshold T may be adjusted (e.g.,increased) based on practical considerations such as consideration ofmultipath channels, and the like. The adjustment amount can bedetermined based on field measurement.

At block 1006, an error rate to be experienced by the given channel canbe predicted based at least in part on the counter determined above. Forexample, the predicted error rate for the given channel can be M′/M.

In some embodiments, a predetermined number of channels can be selectedfrom the plurality of channels by comparing the predicted error ratesfor the plurality of channels with one or more predetermined thresholds.The predetermined number can be a minimum number of channels in a hopsetsuch as 15.

FIG. 11 illustrates an exemplary process 1100 for selecting a hopset ofchannels, in accordance with embodiments. Aspects of the process 1100may be performed by one or more processors associated with the FHreceiving device 102, the FH transmitting device 104, or both.

At block 1102, channels with the lowest predicted error rates that isless than a predetermined first threshold. The channels may allavailable channels within a frequency band and the predicted error ratescan be determined based on power data obtained using techniquesdescribed herein. The channels may be ranked or sorted according totheir respective predicted error rates, for example, from the lowest tohighest error rates. The N channels with the lowest error rates may beselected for the hopset, where N is the minimum number of hopset (e.g.,15). The N may be any suitable positive integer. In some examples, N maybe predetermined for a certain frequency band in compliance withrelevant regulations. In some embodiments, the first threshold may be alow threshold for block error rate (BLER).

At block 1104, it is determined whether the number of total selectedchannels from block 1102 is equal to or greater than N. If yes, then thehopset selection process ends at block 1110. Otherwise, at block 1106,channels with the lowest predicted error rates that are between thefirst threshold and a second threshold are selected. The secondthreshold may be higher than the first threshold. In some embodiments,the second threshold may be a high threshold for BLER.

At block 1108, it is determined whether the number of total selectedchannels so far is equal to or greater than N. If yes, then the hopsetselection process ends at block 1110. Otherwise, at block 1112, channelswith the lowest average interference power are selected until N totalchannels have been selected. In some embodiments, the remaining channelsare ranked or sorted according to their respective average interferencepower (which may be obtained as part of the power data) and the topchannels are selected until N total channels are selected.

In some embodiments, a FH link (e.g., the FH link 108 of FIG. 1) isconfigured to support transmissions across multiple frequency bands. Insuch embodiments, the hopset selection techniques described herein canbe extended to select a hopset of channels from different frequencybands. The power data for each of the frequency bands can be obtainedusing the selective measurement techniques described herein. Besidespower data, other factors may be considered in hopset selection, such asdifferent characteristics between different frequency bands includingtransmission power, antenna gain, propagation loss, and the like.

According to various embodiments, techniques are provided forsynchronizing FH channels between two communication devices. Thesynchronization of FH channels can include the synchronization of hopsetbetween devices and the synchronization of the selection of a particularchannel from the hopset.

When a hopset is generated or updated (e.g., by the FH receiving device102), control data including the updated hopset may be transmitted tothe FH transmitting device (e.g., via the reverse link 106). However,due to interference, fading, and other factors, the FH transmittingdevice may fail to receive such control data, leading to differenthopsets being used by the FH transmitting and FH receiving devices. Thetechniques described in the following examples may be used, alone or incombination, to reduce occurrence of such discrepancy. In the followingdiscussion, the transmission of a hopset can include transmission of thechannels within the hopset or transmission of a difference (delta)between an updated hopset and an older hopset, such as the added orremoved channels.

In an example, the FH receiving device repeatedly transmits the hopsetto FH transmitting device (e.g., via the reverse link 106). Failure toreceive the hopset by the FH transmitting device at one time does notnecessarily prevents the FH transmitting device from eventuallyreceiving the correct hopset, e.g., after the FH transmitting deviceresumes normal operation or when the communication environment improves.

In another example, an effective time indicating when a hopset becomeseffective can be transmitted besides the hopset. The effective time canbe set to allow some time for the FH transmitting device to obtain theupdated hopset before the hopset becomes effective. In some embodiments,other timing information such as an expiration time or validity durationassociated with the hopset may be transmitted instead of or in additionto the effective time.

In another example, the hopset can be configured to change at a reducedfrequency. For example, the hopset may be configured to change only inresponse to significant changes in interference. As another example, apredetermined time period must lapse between consecutive hopset changes.

In some embodiments, the synchronization of the selection of channelswithin a hopset may be achieved using timestamps. In an embodiment, thetransmitting device and the receiving device can each maintain atimestamp. The timestamps of the devices can be synchronized viacommunication between the devices. At any given transmission time, thechannel that is selected from the hopset for transmission can be afunction of both the hopset and the timestamp of the respective device.Thus, as long as the hopsets used by the devices are the same, thechannels selected for the transmission and reception of the signals atany given time are also the same.

The systems, devices, and methods described herein can be applied to awide variety of movable objects. As previously mentioned, anydescription herein of an aerial vehicle, such as a UAV, may apply to andbe used for any movable object. Any description herein of an aerialvehicle may apply specifically to UAVs. A movable object of the presentdisclosure can be configured to move within any suitable environment,such as in air (e.g., a fixed-wing aircraft, a rotary-wing aircraft, oran aircraft having neither fixed wings nor rotary wings), in water(e.g., a ship or a submarine), on ground (e.g., a motor vehicle, such asa car, truck, bus, van, motorcycle, bicycle; a movable structure orframe such as a stick, fishing pole; or a train), under the ground(e.g., a subway), in space (e.g., a spaceplane, a satellite, or aprobe), or any combination of these environments. The movable object canbe a vehicle, such as a vehicle described elsewhere herein. In someembodiments, the movable object can be carried by a living subject, ortake off from a living subject, such as a human or an animal. Suitableanimals can include avines, canines, felines, equines, bovines, ovines,porcines, delphines, rodents, or insects.

The movable object may be capable of moving freely within theenvironment with respect to six degrees of freedom (e.g., three degreesof freedom in translation and three degrees of freedom in rotation).Alternatively, the movement of the movable object can be constrainedwith respect to one or more degrees of freedom, such as by apredetermined path, track, or orientation. The movement can be actuatedby any suitable actuation mechanism, such as an engine or a motor. Theactuation mechanism of the movable object can be powered by any suitableenergy source, such as electrical energy, magnetic energy, solar energy,wind energy, gravitational energy, chemical energy, nuclear energy, orany suitable combination thereof. The movable object may beself-propelled via a propulsion system, as described elsewhere herein.The propulsion system may optionally run on an energy source, such aselectrical energy, magnetic energy, solar energy, wind energy,gravitational energy, chemical energy, nuclear energy, or any suitablecombination thereof. Alternatively, the movable object may be carried bya living being.

In some instances, the movable object can be an aerial vehicle. Forexample, aerial vehicles may be fixed-wing aircraft (e.g., airplane,gliders), rotary-wing aircraft (e.g., helicopters, rotorcraft), aircrafthaving both fixed wings and rotary wings, or aircraft having neither(e.g., blimps, hot air balloons). An aerial vehicle can beself-propelled, such as self-propelled through the air. A self-propelledaerial vehicle can utilize a propulsion system, such as a propulsionsystem including one or more engines, motors, wheels, axles, magnets,rotors, propellers, blades, nozzles, or any suitable combinationthereof. In some instances, the propulsion system can be used to enablethe movable object to take off from a surface, land on a surface,maintain its current position and/or orientation (e.g., hover), changeorientation, and/or change position.

The movable object can be controlled remotely by a user or controlledlocally by an occupant within or on the movable object. The movableobject may be controlled remotely via an occupant within a separatevehicle. In some embodiments, the movable object is an unmanned movableobject, such as a UAV. An unmanned movable object, such as a UAV, maynot have an occupant onboard the movable object. The movable object canbe controlled by a human or an autonomous control system (e.g., acomputer control system), or any suitable combination thereof. Themovable object can be an autonomous or semi-autonomous robot, such as arobot configured with an artificial intelligence.

The movable object can have any suitable size and/or dimensions. In someembodiments, the movable object may be of a size and/or dimensions tohave a human occupant within or on the vehicle. Alternatively, themovable object may be of size and/or dimensions smaller than thatcapable of having a human occupant within or on the vehicle. The movableobject may be of a size and/or dimensions suitable for being lifted orcarried by a human. Alternatively, the movable object may be larger thana size and/or dimensions suitable for being lifted or carried by ahuman. In some instances, the movable object may have a maximumdimension (e.g., length, width, height, diameter, diagonal) of less thanor equal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m, or 10 m. Themaximum dimension may be greater than or equal to about: 2 cm, 5 cm, 10cm, 50 cm, 1 m, 2 m, 5 m, or 10 m. For example, the distance betweenshafts of opposite rotors of the movable object may be less than orequal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m, or 10 m.Alternatively, the distance between shafts of opposite rotors may begreater than or equal to about: 2 cm, 5 cm, 10 cm, 50 cm, 1 m, 2 m, 5 m,or 10 m.

In some embodiments, the movable object may have a volume of less than100 cm×100 cm×100 cm, less than 50 cm×50 cm×30 cm, or less than 5 cm×5cm×3 cm. The total volume of the movable object may be less than orequal to about: 1 cm³, 2 cm³, 5 cm³, 10 cm³, 20 cm³, 30 cm³, 40 cm³, 50cm³, 60 cm³, 70 cm³, 80 cm³, 90 cm³, 100 cm³, 150 cm³, 200 cm³, 300 cm³,500 cm³, 750 cm³, 1000 cm³, 5000 cm³, 10,000 cm³, 100,000 cm³ 3, 1 m³,or 10 m³. Conversely, the total volume of the movable object may begreater than or equal to about: 1 cm³, 2 cm³, 5 cm³, 10 cm³, 20 cm³, 30cm³, 40 cm³, 50 cm³, 60 cm³, 70 cm³, 80 cm³, 90 cm³, 100 cm³, 150 cm³,200 cm³, 300 cm³, 500 cm³, 750 cm³, 1000 cm³, 5000 cm³, 10,000 cm³,100,000 cm³, 1 m³, or 10 m³.

In some embodiments, the movable object may have a footprint (which mayrefer to the lateral cross-sectional area encompassed by the movableobject) less than or equal to about: 32,000 cm², 20,000 cm², 10,000 cm²,1,000 cm², 500 cm², 100 cm², 50 cm², 10 cm²or 5 cm². Conversely, thefootprint may be greater than or equal to about: 32,000 cm², 20,000 cm²,10,000 cm², 1,000 cm², 500 cm², 100 cm², 50 cm², 10 cm², or 5 cm².

In some instances, the movable object may weigh no more than 1000 kg.The weight of the movable object may be less than or equal to about:1000 kg, 750 kg, 500 kg, 200 kg, 150 kg, 100 kg, 80 kg, 70 kg, 60 kg, 50kg, 45 kg, 40 kg, 35 kg, 30 kg, 25 kg, 20 kg, 15 kg, 12 kg, 10 kg, 9 kg,8 kg, 7 kg, 6 kg, 5 kg, 4 kg, 3 kg, 2 kg, 1 kg, 0.5 kg, 0.1 kg, 0.05 kg,or 0.01 kg. Conversely, the weight may be greater than or equal toabout: 1000 kg, 750 kg, 500 kg, 200 kg, 150 kg, 100 kg, 80 kg, 70 kg, 60kg, 50 kg, 45 kg, 40 kg, 35 kg, 30 kg, 25 kg, 20 kg, 15 kg, 12 kg, 10kg, 9 kg, 8 kg, 7 kg, 6 kg, 5 kg, 4 kg, 3 kg, 2 kg, 1 kg, 0.5 kg, 0.1kg, 0.05 kg, or 0.01 kg.

In some embodiments, a movable object may be small relative to a loadcarried by the movable object. The load may include a payload and/or acarrier, as described in further detail elsewhere herein. In someexamples, a ratio of a movable object weight to a load weight may begreater than, less than, or equal to about 1:1. In some instances, aratio of a movable object weight to a load weight may be greater than,less than, or equal to about 1:1. Optionally, a ratio of a carrierweight to a load weight may be greater than, less than, or equal toabout 1:1. When desired, the ratio of an movable object weight to a loadweight may be less than or equal to: 1:2, 1:3, 1:4, 1:5, 1:10, or evenless. Conversely, the ratio of a movable object weight to a load weightcan also be greater than or equal to: 2:1, 3:1, 4:1, 5:1, 10:1, or evengreater.

In some embodiments, the movable object may have low energy consumption.For example, the movable object may use less than about: 5 W/h, 4 W/h, 3W/h, 2 W/h, 1 W/h, or less. In some instances, a carrier of the movableobject may have low energy consumption. For example, the carrier may useless than about: 5 W/h, 4 W/h, 3 W/h, 2 W/h, 1 W/h, or less.

Optionally, a payload of the movable object may have low energyconsumption, such as less than about: 5 W/h, 4 W/h, 3 W/h, 2 W/h, 1 W/h,or less.

The UAV can include a propulsion system having four rotors. Any numberof rotors may be provided (e.g., one, two, three, four, five, six, ormore). The rotors, rotor assemblies, or other propulsion systems of theunmanned aerial vehicle may enable the unmanned aerial vehicle tohover/maintain position, change orientation, and/or change location. Thedistance between shafts of opposite rotors can be any suitable length.For example, the length can be less than or equal to 2 m, or less thanequal to 5 m. In some embodiments, the length can be within a range from40 cm to 1 m, from 10 cm to 2 m, or from 5 cm to 5 m. Any descriptionherein of a UAV may apply to a movable object, such as a movable objectof a different type, and vice versa.

In some embodiments, the movable object can be configured to carry aload. The load can include one or more of passengers, cargo, equipment,instruments, and the like. The load can be provided within a housing.The housing may be separate from a housing of the movable object, or bepart of a housing for a movable object. Alternatively, the load can beprovided with a housing while the movable object does not have ahousing. Alternatively, portions of the load or the entire load can beprovided without a housing. The load can be rigidly fixed relative tothe movable object. Optionally, the load can be movable relative to themovable object (e.g., translatable or rotatable relative to the movableobject). The load can include a payload and/or a carrier, as describedelsewhere herein.

In some embodiments, the movement of the movable object, carrier, andpayload relative to a fixed reference frame (e.g., the surroundingenvironment) and/or to each other, can be controlled by a terminal. Theterminal can be a remote control device at a location distant from themovable object, carrier, and/or payload. The terminal can be disposed onor affixed to a support platform. Alternatively, the terminal can be ahandheld or wearable device. For example, the terminal can include asmartphone, tablet, laptop, computer, glasses, gloves, helmet,microphone, or suitable combinations thereof. The terminal can include auser interface, such as a keyboard, mouse, joystick, touchscreen, ordisplay. Any suitable user input can be used to interact with theterminal, such as manually entered commands, voice control, gesturecontrol, or position control (e.g., via a movement, location or tilt ofthe terminal).

The terminal can be used to control any suitable state of the movableobject, carrier, and/or payload. For example, the terminal can be usedto control the position and/or orientation of the movable object,carrier, and/or payload relative to a fixed reference from and/or toeach other. In some embodiments, the terminal can be used to controlindividual elements of the movable object, carrier, and/or payload, suchas the actuation assembly of the carrier, a sensor of the payload, or anemitter of the payload. The terminal can include a wirelesscommunication device adapted to communicate with one or more of themovable object, carrier, or payload.

The terminal can include a suitable display unit for viewing informationof the movable object, carrier, and/or payload. For example, theterminal can be configured to display information of the movable object,carrier, and/or payload with respect to position, translationalvelocity, translational acceleration, orientation, angular velocity,angular acceleration, or any suitable combinations thereof. In someembodiments, the terminal can display information provided by thepayload, such as data provided by a functional payload (e.g., imagesrecorded by a camera or other image capturing device).

Optionally, the same terminal may both control the movable object,carrier, and/or payload, or a state of the movable object, carrierand/or payload, as well as receive and/or display information from themovable object, carrier and/or payload. For example, a terminal maycontrol the positioning of the payload relative to an environment, whiledisplaying image data captured by the payload, or information about theposition of the payload. Alternatively, different terminals may be usedfor different functions. For example, a first terminal may controlmovement or a state of the movable object, carrier, and/or payload whilea second terminal may receive and/or display information from themovable object, carrier, and/or payload. For example, a first terminalmay be used to control the positioning of the payload relative to anenvironment while a second terminal displays image data captured by thepayload. Various communication modes may be utilized between a movableobject and an integrated terminal that both controls the movable objectand receives data, or between the movable object and multiple terminalsthat both control the movable object and receives data. For example, atleast two different communication modes may be formed between themovable object and the terminal that both controls the movable objectand receives data from the movable object.

FIG. 12 illustrates a movable object 1200 including a carrier 1202 and apayload 1204, in accordance with embodiments. Although the movableobject 1200 is depicted as an aircraft, this depiction is not intendedto be limiting, and any suitable type of movable object can be used, aspreviously described herein. One of skill in the art would appreciatethat any of the embodiments described herein in the context of aircraftsystems can be applied to any suitable movable object (e.g., an UAV). Insome instances, the payload 1204 may be provided on the movable object1200 without requiring the carrier 1202. The movable object 1200 mayinclude propulsion mechanisms 1206, a sensing system 1208, and acommunication system 1210.

The propulsion mechanisms 1206 can include one or more of rotors,propellers, blades, engines, motors, wheels, axles, magnets, or nozzles,as previously described. The movable object may have one or more, two ormore, three or more, or four or more propulsion mechanisms. Thepropulsion mechanisms may all be of the same type. Alternatively, one ormore propulsion mechanisms can be different types of propulsionmechanisms. The propulsion mechanisms 1206 can be mounted on the movableobject 1200 using any suitable means, such as a support element (e.g., adrive shaft) as described elsewhere herein. The propulsion mechanisms1206 can be mounted on any suitable portion of the movable object 1200,such on the top, bottom, front, back, sides, or suitable combinationsthereof.

In some embodiments, the propulsion mechanisms 1206 can enable themovable object 1200 to take off vertically from a surface or landvertically on a surface without requiring any horizontal movement of themovable object 1200 (e.g., without traveling down a runway). Optionally,the propulsion mechanisms 1206 can be operable to permit the movableobject 1200 to hover in the air at a specified position and/ororientation. One or more of the propulsion mechanisms 1200 may becontrolled independently of the other propulsion mechanisms.Alternatively, the propulsion mechanisms 1200 can be configured to becontrolled simultaneously. For example, the movable object 1200 can havemultiple horizontally oriented rotors that can provide lift and/orthrust to the movable object. The multiple horizontally oriented rotorscan be actuated to provide vertical takeoff, vertical landing, andhovering capabilities to the movable object 1200. In some embodiments,one or more of the horizontally oriented rotors may spin in a clockwisedirection, while one or more of the horizontally rotors may spin in acounterclockwise direction. For example, the number of clockwise rotorsmay be equal to the number of counterclockwise rotors. The rotation rateof each of the horizontally oriented rotors can be varied independentlyin order to control the lift and/or thrust produced by each rotor, andthereby adjust the spatial disposition, velocity, and/or acceleration ofthe movable object 1200 (e.g., with respect to up to three degrees oftranslation and up to three degrees of rotation).

The sensing system 1208 can include one or more sensors that may sensethe spatial disposition, velocity, and/or acceleration of the movableobject 1200 (e.g., with respect to up to three degrees of translationand up to three degrees of rotation). The one or more sensors caninclude global positioning system (GPS) sensors, motion sensors,inertial sensors, proximity sensors, or image sensors. The sensing dataprovided by the sensing system 1208 can be used to control the spatialdisposition, velocity, and/or orientation of the movable object 1200(e.g., using a suitable processing unit and/or control module, asdescribed below). Alternatively, the sensing system 1208 can be used toprovide data regarding the environment surrounding the movable object,such as weather conditions, proximity to potential obstacles, locationof geographical features, location of manmade structures, and the like.

The communication system 1210 enables communication with terminal 1212having a communication system 1214 via wireless signals 1216. Thecommunication systems 1210, 1214 may include any number of transmitters,receivers, and/or transceivers suitable for wireless communication. Thecommunication may be one-way communication; such that data can betransmitted in only one direction. For example, one-way communicationmay involve only the movable object 1200 transmitting data to theterminal 1212, or vice-versa. The data may be transmitted from one ormore transmitters of the communication system 1210 to one or morereceivers of the communication system 1212, or vice-versa.Alternatively, the communication may be two-way communication, such thatdata can be transmitted in both directions between the movable object1200 and the terminal 1212. The two-way communication can involvetransmitting data from one or more transmitters of the communicationsystem 1210 to one or more receivers of the communication system 1214,and vice-versa.

In some embodiments, the terminal 1212 can provide control data to oneor more of the movable object 1200, carrier 1202, and payload 1204 andreceive information from one or more of the movable object 1200, carrier1202, and payload 1204 (e.g., position and/or motion information of themovable object, carrier or payload; data sensed by the payload such asimage data captured by a payload camera). In some instances, controldata from the terminal may include instructions for relative positions,movements, actuations, or controls of the movable object, carrier and/orpayload. For example, the control data may result in a modification ofthe location and/or orientation of the movable object (e.g., via controlof the propulsion mechanisms 1206), or a movement of the payload withrespect to the movable object (e.g., via control of the carrier 1202).The control data from the terminal may result in control of the payload,such as control of the operation of a camera or other image capturingdevice (e.g., taking still or moving pictures, zooming in or out,turning on or off, switching imaging modes, change image resolution,changing focus, changing depth of field, changing exposure time,changing viewing angle or field of view). In some instances, thecommunications from the movable object, carrier and/or payload mayinclude information from one or more sensors (e.g., of the sensingsystem 1208 or of the payload 1204). The communications may includesensed information from one or more different types of sensors (e.g.,GPS sensors, motion sensors, inertial sensor, proximity sensors, orimage sensors). Such information may pertain to the position (e.g.,location, orientation), movement, or acceleration of the movable object,carrier and/or payload. Such information from a payload may include datacaptured by the payload or a sensed state of the payload. The controldata provided transmitted by the terminal 1212 can be configured tocontrol a state of one or more of the movable object 1200, carrier 1202,or payload 1204. Alternatively or in combination, the carrier 1202 andpayload 1204 can also each include a communication module configured tocommunicate with terminal 1212, such that the terminal can communicatewith and control each of the movable object 1200, carrier 1202, andpayload 1204 independently.

In some embodiments, the movable object 1200 can be configured tocommunicate with another remote device in addition to the terminal 1212,or instead of the terminal 1212. The terminal 1212 may also beconfigured to communicate with another remote device as well as themovable object 1200. For example, the movable object 1200 and/orterminal 1212 may communicate with another movable object, or a carrieror payload of another movable object. When desired, the remote devicemay be a second terminal or other computing device (e.g., computer,laptop, tablet, smartphone, or other mobile device). The remote devicecan be configured to transmit data to the movable object 1200, receivedata from the movable object 1200, transmit data to the terminal 1212,and/or receive data from the terminal 1212. Optionally, the remotedevice can be connected to the Internet or other telecommunicationsnetwork, such that data received from the movable object 1200 and/orterminal 1212 can be uploaded to a web site or server.

FIG. 13 is a schematic illustration by way of block diagram of a system1300 for controlling a movable object, in accordance with embodiments.The system 1300 can be used in combination with any suitable embodimentof the systems, devices, and methods disclosed herein. The system 1300can include a sensing module 1302, processing unit 1304, non-transitorycomputer readable medium 1306, control module 1308, and communicationmodule 1310.

The sensing module 1302 can utilize different types of sensors thatcollect information relating to the movable objects in different ways.Different types of sensors may sense different types of signals orsignals from different sources. For example, the sensors can includeinertial sensors, GPS sensors, proximity sensors (e.g., lidar), orvision/image sensors (e.g., a camera). The sensing module 1302 can beoperatively coupled to a processing unit 1304 having a plurality ofprocessors. In some embodiments, the sensing module can be operativelycoupled to a transmission module 1312 (e.g., a Wi-Fi image transmissionmodule) configured to directly transmit sensing data to a suitableexternal device or system. For example, the transmission module 1312 canbe used to transmit images captured by a camera of the sensing module1302 to a remote terminal.

The processing unit 1304 can have one or more processors, such as aprogrammable or non-programmable processor (e.g., a central processingunit (CPU), a microprocessor, an FPGA, an application—specificintegrated circuit (ASIC)). The processing unit 1304 can be operativelycoupled to a non-transitory computer readable medium 1306. Thenon-transitory computer readable medium 1306 can store logic, code,and/or program instructions executable by the processing unit 1304 forperforming one or more steps. The non-transitory computer readablemedium can include one or more memory units (e.g., removable media orexternal storage such as an SD card or random access memory (RAM)). Insome embodiments, data from the sensing module 1302 can be directlyconveyed to and stored within the memory units of the non-transitorycomputer readable medium 1306. The memory units of the non-transitorycomputer readable medium 1306 can store logic, code and/or programinstructions executable by the processing unit 1304 to perform anysuitable embodiment of the methods described herein. The memory unitscan store sensing data from the sensing module to be processed by theprocessing unit 1304. In some embodiments, the memory units of thenon-transitory computer readable medium 1306 can be used to store theprocessing results produced by the processing unit 1304.

In some embodiments, the processing unit 1304 can be operatively coupledto a control module 1308 configured to control a state of the movableobject. For example, the control module 1308 can be configured tocontrol the propulsion mechanisms of the movable object to adjust thespatial disposition, velocity, and/or acceleration of the movable objectwith respect to six degrees of freedom. Alternatively or in combination,the control module 1308 can control one or more of a state of a carrier,payload, or sensing module.

The processing unit 1304 can be operatively coupled to a communicationmodule 1310 configured to transmit and/or receive data from one or moreexternal devices (e.g., a terminal, display device, or other remotecontroller). Any suitable means of communication can be used, such aswired communication or wireless communication. For example, thecommunication module 1310 can utilize one or more of local area networks(LAN), wide area networks (WAN), infrared, radio, WiFi, point-to-point(P2P) networks, telecommunication networks, cloud communication, and thelike. Optionally, relay stations, such as towers, satellites, or mobilestations, can be used. Wireless communications can be proximitydependent or proximity independent. In some embodiments, line-of-sightmay or may not be required for communications. The communication module1310 can transmit and/or receive one or more of sensing data from thesensing module 1302, processing results produced by the processing unit1304, predetermined control data, user commands from a terminal orremote controller, and the like.

The components of the system 1300 can be arranged in any suitableconfiguration. For example, one or more of the components of the system1300 can be located on the movable object, carrier, payload, terminal,sensing system, or an additional external device in communication withone or more of the above. Additionally, although FIG. 13 depicts asingle processing unit 1304 and a single non-transitory computerreadable medium 1306, one of skill in the art would appreciate that thisis not intended to be limiting, and that the system 1300 can include aplurality of processing units and/or non-transitory computer readablemedia. In some embodiments, one or more of the plurality of processingunits and/or non-transitory computer readable media can be situated atdifferent locations, such as on the movable object, carrier, payload,terminal, sensing module, additional external device in communicationwith one or more of the above, or suitable combinations thereof, suchthat any suitable aspect of the processing and/or memory functionsperformed by the system 1300 can occur at one or more of theaforementioned locations.

While some embodiments of the present disclosure have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the disclosure. It should beunderstood that various alternatives to the embodiments of thedisclosure described herein may be employed in practicing thedisclosure. It is intended that the following claims define the scope ofthe invention and that methods and structures within the scope of theseclaims and their equivalents be covered thereby.

What is claimed is:
 1. A communication method, comprising: obtainingpower data associated with a plurality of channels of a frequency band;determining a counter of a set of signal-to-noise ratios (SNRs) for eachof the plurality of channels, the set of SNRs being calculated based atleast in part on power data for the each of the plurality of channels;predicting an error rate for each of the plurality of channels based atleast in part on the counter; and selecting a hopset of channels forfrequency hopping from the plurality of channels based at least in parton the predicted error rates for the plurality of channels.
 2. Themethod of claim 1, wherein the counter is determined based on the set ofSNRs and an SNR threshold.
 3. The method of claim 2, wherein the counterindicates a number of SNRs that exceed the SNR threshold.
 4. The methodof claim 1, wherein the power data associated with the plurality ofchannels comprises power spectral density (PSD) data.
 5. The method ofclaim 4, wherein the PSD data associated with the plurality of channelscomprises at least one of noise power spectral density (NPSD) data orsignal power spectral density (SPSD) data.
 6. The method of claim 1,wherein obtaining the power data comprises: selecting a measurement setincluding one or more measurement channels from the plurality ofchannels, a collective set bandwidth of the measurement set covering thefrequency band; obtaining power data for the measurement set byobtaining power data for each of the one or more measurement channels inthe measurement set; and obtaining the power data for the plurality ofchannels using the power data for the measurement set.
 7. The method ofclaim 6, wherein the plurality of channels comprise a first channel anda second channel that overlaps with the first channel, wherein the firstchannel is in the measurement set and the second channel is not in themeasurement set, and wherein power data for the second channel isobtained based on the power data for the first channel.
 8. The method ofclaim 1, wherein selecting the hopset of channels comprises selecting apredetermined number of channels from the plurality of channels bycomparing the predicted error rates for the plurality of channels withone or more predetermined thresholds.
 9. An unmanned aerial vehicle(UAV), comprising: a memory that stores one or more computer-executableinstructions; and one or more processors configured to access the memoryand execute the computer-executable instructions to perform a methodcomprising: obtaining power data associated with a plurality of channelsof a frequency band; determining a counter of a set of signal-to-noise(SNRs) for each of the plurality of channels, the set of SNRs beingcalculated based at least in part on power data for the each of theplurality of channels; predicting an error rate for each of theplurality of channels based at least in part on the counter; andselecting a hopset of channels for frequency hopping from the pluralityof channels based at least in part on the predicted error rates for theplurality of channels.
 10. The UAV of claim 9, wherein the counter isdetermined based on the set of SNRs and an SNR threshold.
 11. The UAV ofclaim 10, wherein the counter indicates a number of SNRs that exceed theSNR threshold.
 12. The UAV of claim 9, wherein selecting the hopset ofchannels comprises selecting a predetermined number of channels from theplurality of channels by comparing the predicted error rates for theplurality of channels with one or more predetermined thresholds.
 13. TheUAV of claim 9, wherein the hopset of channels is used by the UAV toreceive signals from a remote terminal via an uplink.
 14. The UAV ofclaim 9, wherein the method further comprises transmitting informationabout the hopset of channels to a remote terminal via a downlink withthe remote terminal.
 15. The UAV of claim 9, wherein the method furthercomprises selecting a channel from the hopset of channels for receivingsignals from a remote terminal based on a function of the hopset ofchannels and a timestamp.
 16. A communication system, comprising: amemory that stores one or more computer-executable instructions; and oneor more processors configured to access the memory and execute thecomputer-executable instructions to perform a method comprising:obtaining power data associated with a plurality of channels of afrequency band; determining a counter of a set of signal-to-noise ratios(SNRs) for each of the plurality of channels, the set of SNRs beingcalculated based at least in part on power data for the each of theplurality of channels; predicting an error rate for each of theplurality of channels based at least in part on the counter; andselecting a hopset of channels for frequency hopping from the pluralityof channels based at least in part on the predicted error rates for theplurality of channels.
 17. The system of claim 16, wherein the counteris determined based on the set of SNRs and an SNR threshold.
 18. Thesystem of claim 17, the counter indicates a number of SNRs that exceedthe SNR threshold.
 19. The system of claim 16, wherein selecting thehopset of channels comprises selecting a predetermined number ofchannels from the plurality of channels by comparing the predicted errorrates for the plurality of channels with one or more predeterminedthresholds.
 20. One or more non-transitory computer-readable storagemedia storing computer-executable instructions that, when executed by acomputer system, configure the computing system to perform operationscomprising: obtaining power data associated with a plurality of channelsof a frequency band; determining a counter of a set of signal-to-noiseratios (SNRs) for each of the plurality of channels, the set of SNRsbeing calculated based at least in part on power data for the each ofthe plurality of channels; predicting an error rate for each of theplurality of channels based at least in part on the counter; andselecting a hopset of channels for frequency hopping from the pluralityof channels based at least in part on the predicted error rates for theplurality of channels.